Energy Storage Integration

April 18, 2017

The Inland Empire Utilities Agency (IEUA/Agency) is a regional wastewater treatment agency and wholesale distributor of imported water. The Agency is responsible for serving approximately 875,000 people over 242 square miles in western San Bernardino County, which is located about 30 miles east of Los Angeles in southern California. The Agency is focused on providing three key services: (1) treating wastewater, developing recycled water, local water resources, and conservation programs to reduce the region’s dependence on imported water supplies and drought-proof the service area; (2) converting biosolids and waste products into a high-quality compost made from recycled materials; and (3) generating electrical energy from renewable sources.

As a public agency focused on maximizing water efficiency and reuse, IEUA has spent years navigating the link between water and energy. Treating wastewater and pumping to recycled water users or groundwater replenishment basins greatly improves regional sustainability, but also requires a large amount of energy. Starting in 2008, IEUA embarked on an ambitious campaign to ease electricity demand from the grid by utilizing onsite renewable energy sources. After constructing 3.5 MW of solar, a 1-MW wind turbine, a 2.8-MW fuel cell, and a food waste digestion process powering a 1.5-MW cogeneration engine, IEUA currently derives 50% of its peak electricity demand from renewable power.

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IEUA’s renewable portfolio was strategically established by identifying how available resources, such as wastewater treatment infrastructure and available land, could be used to bring in self-generation technologies that were environmentally friendly and priced at a rate comparable to grid import costs. These renewable power systems were the product of public-private partnerships whereby third-party energy developers constructed power plants at IEUA wastewater treatment plants at no cost to the Agency. IEUA then purchases all the power produced by the renewable systems at a fixed price for an agreed-upon term. This agreement structure allowed IEUA to successfully incorporate a diverse array of technologies into its facilities while expending limited capital and reducing its demand on the grid.

Since installation, each of these technologies has reliably operated as a standalone system with no exchange of information with other power generation sources or overall facility demand. IEUA has not had the ability to control the distribution of power generated until the Agency implemented a new landmark battery storage project design to enhance its energy management portfolio by optimizing these generation sources and identifying cost-effective methods of energy procurement.

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In 2015, IEUA partnered with Advanced Microgrid Solutions (AMS) to install 3.65 MW (7.3 megawatt-hours) of state-of-the-art battery storage across two of IEUA’s pumping stations and four wastewater treatment plants. By communicating with IEUA’s renewable resources and utilizing sophisticated software, the batteries and associated software form a smart energy management system that integrates all power generation sources, reduces energy costs, and provides control and visibility at levels that were previously unattainable. These benefits are what led IEUA to become the first water agency in the nation to incorporate battery storage into its portfolio.

Since the cost of power imported from the electric utility varies with the time of day, savings can be achieved through strategic procurement. The battery storage system is equipped with software that utilizes a learning algorithm to predict facility power needs based on historical consumption data. Using this predictive tool, the storage system can determine optimum schedules for charging and discharging the batteries. Complex electrical utility tariff engines are incorporated to assess and optimize the cost savings achieved through battery operation.

Benefits from the battery storage system are not only realized by IEUA. These systems also prove to be valuable assets to the utility as a means for stabilizing grid demand. Time-of-use energy rates are typically designed to align higher costs with periods of high power demand on the utility. This means that the batteries’ planned schedule of discharging when power costs are highest also aligns with the periods when the grid needs relief the most. In this respect, the battery storage system is not only enhancing the energy management capabilities of the Agency, it is also helping to flatten out the peaks in demand that the grid experiences.

Unlike renewable power generation systems, such as solar or wind, this method of grid relief is not tied to weather patterns. The battery storage can be called upon whenever demand on the utility is highest, regardless of the time of day. This flexibility means that the relief offered by battery storage could even shift with the peak period if needed.

The electric grid has historically seen its highest demands when the ambient temperature is warmest, as space cooling is a very energy-intensive process. This trend resulted in time-of-use rates that peak in the middle of the day during the summer months. Facilities that employ solar power systems can offset peak pricing during these periods of high demand by generating power onsite and avoiding grid imports.

In 2010, IEUA added a 2.8-MW fuel cell system at Regional Water Recycling Plant No. 1 in Ontario, CA.

However, the steady increase of solar installations across the state in the past decade has begun to shift the peak demand. Solar’s impact on grid consumption has reduced the need for imported electricity during the middle of the day and shifted the peak demand to early evenings, when solar systems typically do not generate power. Battery storage can provide a solution to this change in consumer behavior by shifting with the peak. For large energy users with onsite solar generation, such as IEUA, the batteries ensure that renewable energy will continue to achieve savings, regardless of how peak pricing is structured.

IEUA will install 3.65 MW of Tesla battery storage at six IEUA facilities, which is expected to save the Agency approximately $230,000 annually in electricity costs.

Grid relief during normal operation is only one component of the symbiotic link that energy storage forms between the electrical utility and the customer. The batteries also prove to be valuable assets to both parties during demand response events. Historically, when the utility would call upon large energy consumers to curb power usage due to demand on the grid, IEUA would shut off power-intensive processes, such as pumping or aeration. With energy storage, the Agency can discharge from the batteries instead of, or in addition to, altering system processes. The relief allows the electric utility to redistribute IEUA’s energy demand to local customers during a period when the grid is struggling to meet demand. At the same time, IEUA has added flexibility in determining how to either meet or improve its ability to help the grid.

Deployment of the batteries during periods of high grid demand also results in a decrease of greenhouse gas emissions (GHGs). To meet a temporary increase in power demand, electric utilities often use “peaker” power plants that operate strictly to supplement consumer needs. These “peaker” plants often emit GHGs at a rate higher than alternative forms of power generation. Integrating battery storage reduces the need for these temporary systems, and subsequently, the amount of GHGs in the atmosphere.

In June 2016, IEUA’s Regional Water Recycling Plant No. 5 (RP-5) was the first of the six IEUA facilities to complete construction of a battery storage system. A total of 1 MWh of Tesla batteries was successfully integrated into the facility’s electrical profile, which includes a 1-MW solar plant and a 1.5-MW cogeneration engine fueled by anaerobically digested food waste. The facility also imports electricity to meet incremental power needs beyond the site’s renewable generation capacity.

Modeling analysis performed by AMS indicated that the overall project will reduce IEUA’s peak demand from the electric grid by as much as 14% and decrease the Agency’s total energy costs by 5 to 10%. When implemented at all six sites, the batteries are expected to reduce IEUA’s energy costs by as much as $230,000 per year. Through seven months of operation at RP-5, the battery storage system has achieved monthly energy cost savings ranging between 9 to 19%, thus far exceeding expectations. The system’s learning algorithm has performed as expected, as RP-5 cost savings increased each month as the software received more operational data.

Like previous public-private partnerships, the Agency’s agreement with AMS was structured such that IEUA expended no capital outlay for the battery storage systems. Minimal capital investment coupled with ongoing reduced operational costs results in continuous savings for IEUA and its ratepayers.

This project will have a significant positive impact on the water and wastewater industry as well as the nation of renewable power generators by demonstrating the potential benefits that can be achieved through its implementation. IEUA has successfully integrated battery storage into its wastewater treatment facilities and renewable resources, and the lessons learned through this project can play an important role as the innovative technology is applied throughout the industry and broader applications in the future. Although the reliable operation of wastewater treatment plants lends itself to the implementation of battery storage, the technology is easily translatable as long as an industry is consuming power. 
About the Author

P. Joseph Grindstaff

P. Joseph Grindstaff is the general manager for Inland Empire Utilities Agency.